Ultrasound is often used as a tool to guide surgical devices like needles or catheters during minimally invasive procedures. For example, surgical biopsy procedures are commonly performed using ultrasonic imaging to enable the physician to view the tissue being biopsied.
One of the advantages of ultrasound over X-ray imaging for use during a surgical procedure is that it provides soft tissue contrast and depth information, while it does not use ionizing radiation. However, it is often challenging to identify interventional devices in an ultrasound image since many devices such as needles are specular reflectors and do not return the ultrasound beam back to the transducers.
In addition, devices such as catheters may have a similar appearance on ultrasound images as tissue structures, also depending on imaging settings. Various techniques are used to improve the visualization of devices, such as adding echogenic coatings or etching.
The concept of needle tracking in an ultrasound device is known, for example by coating a needle tip with a piezo-material that provides an electrical signal upon “activation” by ultrasound energy. An ultrasonic transducer may alternatively be attached to a biopsy needle to cause the needle to transmit and/or receive ultrasonic waves in cooperation with an imaging scan head.
An alternative to these active approaches is to passively view the biopsy needle using color Doppler images. Hand manipulation of a biopsy needle or guide-wire has been found to provide a color image that corresponds to the shaft of the needle. However, the image of the needle is only highly defined when the needle is being manipulated, and is a coarse representation of the entire needle shaft.
It has been proposed to continually visualize the tip of the needle by mechanically reciprocating the needle. Unsynchronized reciprocation of the biopsy needle (or stylet) causes a constantly changing Moiré pattern when the Doppler representation of the needle tip is displayed in color. A system making use of this technique is described in U.S. Pat. No. 5,095,910.
US2010/0305432 discloses another system and method for locating medical devices in vivo using ultrasound in a 3D Doppler mode. In this method, 3D Doppler imaging is used to detect a medical device coupled to a vibratory element to induce vibrations in the distal end of the device. Different parts of the medical device may be configured to vibrate with different frequencies. This is achieved by segments of material of different densities, which attenuate the vibrations generated by a vibration module at the proximal end.
The concept of vibrational device detection using Real-Time 3D Color Doppler has also been proposed in IEEE Trans Ultrason Ferroelectr Freq Control. 2008; 55(6): 1355-1362.
Various different uses of vibration elements have been proposed, for use in Doppler imaging systems, such as:
providing a vibrating element to a minimally invasive device (catheter, needle, guide-wire) to provide whole body vibrations;
providing a vibrating element at a proximal end (ex vivo) or distal end (in vivo);
using different frequencies at different locations, for example with the frequency altered by changes in material density or more vibrating elements.